In recent years, trucking companies have become more conscious of the costs of fuel consumed by their vehicles, particularly those trucks—which are very often referred to as tractors—whose purpose is to tow a trailer or trailers along the roadway, and especially at high speeds along a highway. While the manufacturers of such trucks are doing their best to improve efficiencies by making their truck designs more aerodynamic, and making their engines more fuel efficient, the fact remains that significant aerodynamic losses occur as a result of trailer design, especially at high speed. The current trailer designs create drag on the trailer due to wind resistance as the trailer moves. Even if the engine and the aerodynamic design of the trucks is improved, there still remains the problem of reducing the drag created by the trailer, so as to thereby increase the fuel efficiency of the towing truck.
Moreover, federal and state authorities in the United States and Canada are increasingly tightening the restrictions as they apply to the trucking industry, requiring more fuel efficiency so as to reduce carbon and greenhouse gas emissions from the trucks. Indeed, the California Air Resources Board has mandated that trailers must manifest lower drag coefficients so as to reduce carbon and greenhouse gas emissions in that state. Other states and provinces will undoubtedly follow suit, although the specific mandated reduction in drag may vary among those various authorities. Thus, even a reduction of drag of, say, 2%, may be acceptable in some states and provinces; whereas other states and provinces, such as California, may require a reduction of drag in the range of 2, 5, or 10%, or more.
One common approach to reduction of drag by trailers has been to fit or retrofit the trailers with fairings mounted along each side. Such fitment or retrofit may, however, be labour intensive as well as requiring considerable expenditure of capital money. Such expenses may be significant to any trucking company or a company which owns and rents trailers, even if the company's trailer inventory is only a few trailers, or possibly several thousand trailers.
Moreover, the fitment of fairings along both sides of a trailer may inhibit the opportunity of the trailer operator to move the wheel set or wheel sets on which the trailer moves. Depending on its intended use and load factors of the trailer, a wheel set may be moved more forwardly or backwardly along the bottom of the trailer for such purposes as balancing the load as well as to accomplish more efficient loading factors on the wheel sets.
The present inventors have unexpectedly discovered that rather than placing fairings along each side of a trailer, the fitment of a drag reduction plate along at least a portion of the length of the trailer forward of the trailers rear wheel set, where the drag reduction plate depends vertically downwardly from the bottom of the trailer, will reduce drag on the trailer. Of course, it is accepted that such installation to a trailer may not affect the same fuel efficiencies as will the fitment of fairings to a trailer, but does, in any event, result in higher fuel efficiencies which may be attained with lower capital cost, lower labour cost, and in faster time. Such an arrangement is most often acceptable to trucking company officials as well as to regulatory officials at the state or provincial levels.
As such, the present inventors have found that the provision of drag reduction plates, as well as other drag reduction structures, may be provided by what is essentially one or more plate-like structures, to the lower surfaces of a trailer. The plate, or plates, may be made of a rigid or semi-rigid material such as steel or aluminum, but more preferably is made of a rigid or semi-rigid material such as a reinforced plastic or fiberglass or composite structure having lower cost and lower weight than a similar steel structure.